Noise & Wireway question

[ssommers 20]

I've been handed a project where the mechanical engineer is going to install a platform for a new induction welder over the top of an existing machine. The problem is that the bottom of the platform will probably barely clear the existing main wireway for the rest of the machine. Oh, and the platform design is already "set" since the final welder design was accepted in February, before I came on board. I know the wireway must be moved for noise immunity and future accessibility (mostly accessibility). Are there any standards I can quote that say how much room is needed around the wireway hatches or recommended distance for noise resistance for the control signals passing by the welder? (All control signals are 120VAC on this machine.) I simply want to make sure that a non-engineering manager understands why I'm going to unwire & rewire the entire machine. He understands such things as "Code requires it." If it gets more complex, I'll have to write up a justification. Thanks, Susan

[BobLfoot 302]

Not as lean as "Code requires it" but what does the Manual for your new Welder specify for clearances between it and other wiring. If you can say "the new machine Installation Manual requires it" aren't you alsmost as good.

[ssommers 20]

Yes, one sentence answers are about the length of this manager's attention span. I'm going to look to see if there's a spec on how far away non-welder wiring must be from the welder. I'm not completely sure yet where the welder is sitting on the platform relative to the current wireway position. I'm much more certain that the wireway hatch won't be able to open if they placed the platform without moving the wireway. I'm still looking for this answer though... Is there a standard or code on how far the hatch on a wireway must be able to open once it's in place? The plant manager would rather build the platform right over the cover of the main wireway and make it inaccessible rather than take an extra 2-3 weeks to unwire the machine, move the wireway to an accessible place, and rewire the machine if it's not required. This will be a slam dunk if it's required by a code or manufacturer's spec. I don't care which because I'm just trying to make the electricians' jobs easier for the next 15 years. Thanks, Susan who remembers being the only one who was able to fit between the conveyor and the electrical panel where the door only opened to 45 deg. Edited 31 Oct 2006 by ssommers

[gravitar 3]

I thumbed through some weld controller books expecting to find some guidance on how to wire them. Surprisingly though, none of them said much! Although it's not welding-specific, I'm sure the NEC has rules to follow on separation of conductors of different voltage threshholds. I KNOW they discuss panel door clearance.. I believe its on the order of 3', but it depends on what it opens up to. (brick wall, another panel, etc.)

[larry818 0]

110.26 covers enclosure clearances, but only applies to enclosures "likely to require examination, adjustment, servicing, or maintenance while energized". There's no requirement outside of this article that you even leave enough room to open the door. A friend of mine was working for a welding machine manufacturer and was brought on to solve problems with the welders inducing noise into their own controls. He solved the problem and started to do testing to create a standard for their controls design and external wiring, which had never been done, when they laid him off. You might look to the eu for standards, as they are better about this kind of thing than we are. There are no US codes covering this. You'd be lucky to find this info from the welder mfg. Edited 22 Nov 2006 by larry818

[newpageboba 7]

Rockwell has a 'Wiring and Grounding Guide, (PWM) AC Drives' Publication #DRIVES-IN001E-EN-P It has guidlines for AC Drive installation. Chapter 4 page 4-9 has a table for Wire routing recommendations. They also talk about cable type and grounding practices. You want to watch out for noise that the welder introduces into your control wiring (good reason to relocate your wireway). It doesn't cover welders, but you should be able to get some answers here. The NEC code book does cover minimum distance between cable types (ie. voltage level, signal type, etc.), just can't remember where. Good Luck

[robh 12]

What type of wireway is being used? NEC 110.26.A covers this. (I C larry already said this!) NEC 630 covers eletric welders Edited 22 Nov 2006 by robh

[ssommers 20]

Thanks for all the great input... NEC 665 applies to Induction Welders which is what I'm installing. I'm getting rid of a Resistance Welder, NEC 630. The type of wireway I'm using for the bulk of the machine is Hammond Manufacturing 1485D120 (6"x6"x10') lay-in wireway. I'm putting a barrier inside that to separate the 480 & 120 VAC. Separate conduits will be run for 24 & 10 VDC signals. All DC signals will be shielded cables. There is a special conduit with 4 300mcm wires & 1 4/0 ground wire from the welder power supply enclosure to the high frequency solid state welder which will run parallel to the wireway for a short distance. This is the one I'm concerned about inducing noise in the other wireway & conduits. I searched Mike Holt's Code Forum found 12" as a recommended separation of voltages for noise reduction. There's nothing in the manufacturer's installation literature on routing of this conduit, but it's going to be installed in the shortest route possible. Anyone else have a spec (Code or company policy) or rule of thumb that I can use besides 12"? Thanks for everyone's input, Susan